Evolution of the exchange properties of a K-beidellite submitted to alternate wetting and drying cycles

Mohamed Larid, Hachemi Zaidi, Abdellah Bakhti

Abstract: Many studies have shown that smectites, particularly under the effect of drying, could be one of the causes of the retrogradation of potassium (K) in the soil. Most of these studies have focused on the fixation of K in montmorillonites with an octahedral charge deficit. However, smectites most often have both tetrahedral and octahedral charge deficits. This led us to study the variation in K exchangeability for a K-beidellite during wetting and drying (WD) treatment. Chemical analysis and X-ray diffraction showed that, the fine fraction of the studied raw clay is a mixed beidellite, where 70% of the charge comes from substitution in the tetrahedral layer. The study in the variation of K exchange capacity for K-beidellite as a function of the number of WD cycles, allowed to show that the amount of fixed K is related both to the number of WD cycles and to the negative charges arising from the substitution in the octahedral sheets.

Keywords: beidellite; exchange; potassium; wetting and drying

Date published: 2019-03-29